A position sensor is a device that can detect the presence and location of a touch, by a user's finger or by an object, such as a stylus, for example, within a display area of the position sensor display screen. In a touch sensitive display application, the position sensor enables a user to interact directly with what is displayed on the screen, rather than indirectly with a mouse or touchpad. Position sensors can be attached to or provided as part of computers, personal digital assistants (PDAs), satellite navigation devices, mobile telephones, portable media players, portable game consoles, public information kiosks, point of sale systems, and the like. Position sensors have also been used as control panels on various appliances.
There are a number of different types of position sensors/touch screens, such as resistive touch screens, surface acoustic wave touch screens, capacitive touch screens, and the like. A capacitive touch screen, for example, may include an insulator, coated with a transparent conductor in a particular pattern. When an object, such as a user's finger or a stylus, touches or is provided in close proximity to the surface of the screen there is a change in capacitance. This change in capacitance is sent to a controller for processing to determine the position of the touch.
An array of drive (in one example X) electrodes and sense (in this example Y) electrodes of conductive material can be used to form a touch screen having a plurality of nodes, a node being formed at each intersection of X and Y electrodes. Applying a voltage across the array of electrodes creates a grid of capacitors. When an object touches or is provided in close proximity to the surface of the screen, the capacitance change at every individual point on the grid can be measured to determine the location of the touch.
In recent years, two-dimensional position sensors have been developed. It is desirable for position sensors to be scalable so that they can be used in large screens. In addition, it is desirable for position sensors to be as thin as possible.